This invention relates to a cable splice for an electrical cable and to a method for making a cable splice. More particularly, this invention relates to a cable splice for use in high temperature, high pressure gassy oil wells adapted to prevent corrosive attack on the conductors by sulfide gases and to a method for making said cable splices.
In general, cable structures employed for oil well service have stranded metallic conductors, usually formed of copper, separately insulated with a material of high dielectric strength, cabled and surrounded by an outer armor. In joining cable sections, a splice is formed between the conductors comprising a metallic member frictionally engaging the conductors which is insulated by a section of insulant surrounding any remaining exposed areas of the conductors and the metallic member. The section of insulant typically is formed by a plurality of layers of insulating tape, which may be further protected and confined by a heat shrinkable sleeve positioned over the splice insulation and extending over the adjacent insulation to seal the splice area.
Where the well cable is to be employed in wells containing corrosive gases, particularly sulfides, invasion of the cable structure by corrosive well fluids under high pressure occurs either by way of pinholes or other defects in the primary insulation of the cable or by gas permeation. The conductors are particularly susceptible to attack and corrosion by the sulfides, which results in destruction of the conductors and a shortened cable life.
One method for preventing sulfide attack on the conductors has been the sheathing of the conductor and insulation with a sulfide-impervious layer such as metallic lead. The lead sheath acts as a barrier to exclude the sulfide-containing fluids from the cable structure. In splicing such lead-sheath conductors, it has been the practice to cover the insulated splice with an outer casing formed of heavy gauge lead sheet. The outer casing is soldered to the lead cable sheath at each end of the splice and along the casing seam to seal the splice area and prevent the invasion of corrosive fluids. In practice, and particularly under field conditions, the forming and soldering of the lead casing is a slow and difficult operation to carry out. Damage to the cable insulation can occur through application of excessive heat during the soldering operation, and forming perfect solder joints under field conditions, is difficult, increasing the possibility of invasion of the splice area by corrosive fluids.
A method for forming a cable splice between lead sheathed conductors which would provide a substantial barrier to the intrusion of well-fluids and which could be carried out rapidly under field conditions would thus be a useful advance in the art.